There exist many apparatuses for rotating caps relatively to a container. For example, such apparatuses are used for screwing caps onto containers or screwing off caps from containers.
Some of these apparatuses include discs that rotate in opposing directions. For example, U.S. Pat. No. 5,918,442 issued to Dewees on Jul. 6, 1999, describes such an apparatus. In these apparatuses, a container is moved toward the discs and the cap is positioned over the container. When the cap reaches the discs, the discs engage the cap and rotate the discs relatively to the container.
Since there is typically a need to rotate the cap by a relatively large angle, the discs must rotate relatively fast because the duration of the engagement between the discs and the cap is relatively short. This causes the discs to wear relatively fast. In addition, having discs that rotate at a relatively high speed tends to destabilize the container when the cap is engaged as an impact produced onto the cap by the discs is then transmitted to the container. Furthermore, when a cap is screwed onto a container, the discs typically do not allow adjusting relatively precisely a torque applied to the cap.
In another type of device used for screwing caps onto containers, two belts are used to apply forces onto opposite sides of a cap. An example of such a device is found in U.S. Pat. No. 3,280,534 issued to Hildebrandt et al. on Jan. 4, 1963. Once again, achieving a relatively precise torque when screwing the cap is relatively hard to achieve using these types of devices. Also, the speed of the belt is usually fixed. Therefore, it is relatively hard to select belt speeds that are suitable for both rotating the cap relatively fast when the cap is initially screwed onto the container and producing a relatively slow rotation of the cap when the cap is almost entirely screwed onto the container.
Indeed, as the cap is screwed onto the container, a torque applied by the rotating cap onto the container increases. At one point, the cap will slide relatively to the belts because typically, the force that is applied onto the cap is smaller than a force applied onto the container that resists rotation. A slipping belt wears off prematurely, may damage the cap and may destabilize the container.
Against this background, there exists a need in the industry to provide a novel apparatus and method for rotating a cap relatively to a container.